Houses here will appreciate moderately for the rest of 1980, but not at the dizzying double-digit rates of recent years, veteran appraisers predict.

They suggest that 8 percent may be the average rise for the year, well below the 12 to 16 percent that have prevailed throughout the metropolitian area since late 1977. Appraisers also warn that large, expensive houses in suburban subdivisions -- properties valued at $200,000 and above in such sections as Potomac and McLean -- will probably gain in value at a slower rate than the average for the area.

On the other hand, small houses and condominium apartments convenient to public transportation are likely to appreciate at rates several points above the average, appraisers predict.

William S. Harps, first vice president of the John R. Pinkett, Inc., realty firm, says Washington area property owners "should be prepared for the decelerating price cycle we're in," and should adjust their resale expectations accordingly. Harps expects houses values to increase 5 to 10 percent here this year.

In historic terms, "that sort of rise is very favorable," Harps points out, but owners who have gotten used to the record-setting price increases of the last four years "may have assumed that these rates could continue forever."

Harps has studied Alexandria, the District and other jurisdictions recently and has found that mortgage rates of 1o percent and minimal growth in families' disposable incomes have helped flatten house prices. Nothing on the horizon is likely to turn this around for the next two months, he says.

Higher-priced houses have stopped rising in resale value, Harps notes, because not that many purchasers out there can handle the mortgage payment of $2,000 to $2,500 a month required by a $175,000 to $200,000 conventional loan at 13 to 14 percent. Even with large down payments financed with the proceeds from earlier house sales, Harps said, the sheer monthly cast drains required for houses costing over $175,000 "are acting as a weight against any immediate, substantial increases in that segment of the market."

Moderate-priced houses are keeping up in resale value because they appeal to a much larger segment of the market -- including buyers turned away from larger properties by the costs of acquisition.

Alfred W. Jarchow, an appraiser in Rockville whose monthly studies of Montgomery County properties track price movements in all major neighborhoods, said the growing surplus of high-cost homes and the shortgage of moderate-cost units virtually ensures faster appreciation rates for the latter. This includes well-located condominium units and subdivision houses and represents a reversal of the pattern of three years ago, when the upper-bracket properties were most in demand.

Jarchow thinks that 8 percent is a realistic planning number for owners in the area looking ahead to a sale in 1980. Prices are likely to remain flat -- as Jarchow's graphs show them to have been for the past 90 days -- until demand perks up in the spring. Assuming mortgage money is available at rates no higher than today's, and the national economy doesn't fall apart, the spring and summer ought to register 5 to 8 percent increases. The autumn months should add another 2 to 3 percentage points on to the total for a typical suburban home in the area, using Jarchow's scales.

Well-located, distinctive properties inside the District probably will outpace similarly priced units in communities well beyond the Beltway, appraisers agree. The demand for homes in select neighborhoods of Northwest, such as Cleveland Park and Forest Hills, appears to be more resilient than in the suburbs.

The costs of commuting and convenience to business and cultural attractions are key factors in the appeal of the Northwest. Some families are seeking to move in from large homes in the outlying suburbs, thereby adding to the surplus of unsold houses outside the Beltway, and increasing demand inside the District.

Worthington B. Houghton, president of A. C. Houghton & Son, Inc., notes that while price increases may moderate temporarily because of high mortgage costs and a softening economy, "the long-term picture here is for continued, substantial appreciation in values.

"All the basic real estate factors for Washington are positive," Houghton said: "Income growth here is far above most parts of the country, two-income families continue to play an important role in overall household composition, property values here are still below those prevailing in western European countries, and the demand for ownership is very high -- as a safeguard against inflation and the income tax system."

The after-tax yields on residential and investment housing -- thanks to favorable tax policies enacted by Congress -- easily outpace inflation, even when appreciation rates moderate to 1980's projected levels, Houghton noted.